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Online dispute resolution is becoming the main method when dealing with a conflict in e-commerce. A family of defeasible reasoning patterns is used to provide a useful link between dispute resolution agents and legal doctrines. The proposed argumentation framework combines defeasible logic with temporal reasoning and argumentation with level of certainty. The evaluation of arguments depends on the stage of the dispute: commencement, discovery, pre-trial, arbitration, according to current practice in law. By applying the open world assumption to the rules, the argumentative semantics of defeasible logic is enriched with three types of negated rules which offer symmetrical means of argumentation for both disputants. A corollary of this extension consists in defining a specialized type of undercutting defeater. The theory is illustrated with the help of a concrete business-to-client case in a prototype implemented system. [ABSTRACT FROM AUTHOR]

We present a novel approach to knowledge-based automated one-shot multi-issue bilateral negotiation handling, in a homogeneous setting, both numerical features and non-numerical ones. The framework makes possible to formally represent typical situations in real e-marketplaces such as "if I spend more than 20000 € for a sedan then I want a navigator pack included" where both numerical (price) and non-numerical (sedan, navigator pack) issues coexist. To this aim we introduce $\mathcal{P}(\mathcal{N})$, a propositional logic extended with concrete domains, which allows to: model relations among issues (both numerical and not numerical ones) via logical entailment, differently from well-known approaches that describe issues as uncorrelated; represent buyer's request, seller's supply and their respective preferences as formulas endowed with a formal semantics. By modeling preferences as formulas it is hence possible to assign a utility value also to a bundle of issues, which is obviously more realistic than the trivial sum of utilities assigned to single elements in the bundle itself. We illustrate the theoretical framework, the logical language, the one-shot negotiation protocol we adopt, and show we are able to compute Pareto-efficient outcomes, using a mediator to solve a multi-objective optimization problem. [ABSTRACT FROM AUTHOR]

We address the problem of standardising the semantics of agent communication. The diversity of existing approaches suggests that no single agent communication language can satisfactorily cater for all scenarios. However, standardising the way in which different languages are specified is a viable alternative. We describe a standard meta-language in which the rules of an arbitrary institution can be specified. In this way different agent communication languages can be given a common grounding. From this starting point, we describe a component based approach to standardisation, whereby a standard can develop by adding component sets of rules; for example to handle various classes of dialogs and normative relations. This approach is illustrated by example. Eventually we envisage different agent institutions publishing a specification of their rules by simply specifying the subset of standard components in use in that institution. Agents implementing the meta-language can then interoperate between institutions by downloading appropriate components. [ABSTRACT FROM AUTHOR]

Development of more complex cognitive systems during evolution is sometimes viewed in relation to environmental complexity. In more detail, growth of complexity during evolution can be considered for the dynamics of externally observable behaviour of agents, for their internal cognitive systems, and for the environment. This paper explores temporal complexity for these three aspects, and their mutual dependencies. A number of example scenarios have been formalised in a declarative temporal language, and the complexity of the structure of the different formalisations was measured. Thus, some empirical evidence was provided for the thesis that for more complex environments, more complex behaviour and more complex mental capabilities are needed. [ABSTRACT FROM AUTHOR]

Some issues concerning beliefs of agents are discussed. These issues are the general syntactic form of beliefs, the logic underlying beliefs, acquiring beliefs, and reasoning with beliefs. The logical setting is more expressive and aspects of the reasoning and acquisition processes are more general than are usually considered. [ABSTRACT FROM AUTHOR]

Decision-making is a fundamental feature of agent systems. Agents need to respond to requests from other agents, to react to environmental changes, and to prioritize and pursue their goals. Such decisions can have ongoing effects, as the future behavior of an agent may be heavily dependent on choices made earlier. In this paper we investigate a formal framework for modeling the choices of an agent. In particular, we show how the use of a choices calculus based on temporal linear logic can be used to capture distribution, temporal and dependency aspects of choices. [ABSTRACT FROM AUTHOR]

Agent-oriented programming languages have gone a long way in the level of sophistication offered to programmers, and there has also been much progress in tools to support multi-agent systems development using such languages. However, much work is still required in mechanisms that can reduce the burden, typically placed on programmers, of ensuring that agents behave rationally, hence being effective and as efficient as possible. One such mechanisms is reasoning about declarative goals, which is increasingly appearing in the agents literature; it allows agents to make better use of resources, to avoid plans hindering the execution of other plans, and to be able to take advantage of opportunities for reducing the number of plans that have to be executed to achieve certain combinations of goals. In this paper, we introduce a Petri-net based approach to such reasoning, and we report on experimental results showing that this technique can obtain comparable improvements on an agent's behaviour to other existing approaches (our experiments do not yet cover reasoning about resource usage). Our long-term goal is to provide a number of alternative approaches for such reasoning, evaluate and compare their performances under different configurations, and incorporate them into interpreters for agent-oriented programming languages in such a way that the most appropriate approach is used at given circumstances. [ABSTRACT FROM AUTHOR]

We present a mechanism to detect and resolve conflicts in virtual environments, populated by agents whose behaviours are regulated by norms, that is, explicit representations of obligations, permissions and prohibitions. A conflict arises when an action is simultaneously prohibited and obliged/permitted. We use first-order unification and constraint satisfaction to detect and resolve such conflicts, introducing a concept of norm curtailment. We present an algorithm for norm adoption which preserves conflict-freedom. Our approach allows us to address indirect conflicts and conflicts arising from the delegation of actions between agents. [ABSTRACT FROM AUTHOR]

A rational agent derives its choice of action from its beliefs and goals. Goals can be distinguished into achievement goals and maintenance goals. The aim of this paper is to define a mechanism which ensures the satisfaction of maintenance goals. We argue that such a mechanism requires the agent to look ahead, in order to make sure that the execution of actions does not lead to a violation of a maintenance goal. That is, maintenance goals may constrain the agent in choosing its actions. We propose a formal semantics of maintenance goals based on the notion of lookahead, and analyze the semantics by proving some properties. Additionally, we discuss the issue of achievement goal revision, in case the maintenance goals are so restrictive that all courses of action for satisfying achievement goals will lead to a violation of maintenance goals. [ABSTRACT FROM AUTHOR]

Research on practical models of autonomous agents has largely focused on a procedural view of goal achievement. This allows for efficient implementations, but prevents an agent from reasoning about alternative courses of action for the achievement of its design objectives. In this paper we show how a procedural agent model can be modified to allow an agent to compose existing plans into new ones at runtime to achieve desired world states. This new agent model can be used to implement a declarative goals interpreter, since it allows designers to specify only the desired world states in addition to an agent's basic capabilities, enhancing the agent's ability to deal with failures. Moreover our approach allows the new plans to be included in the plan library, effectively enabling the agent to improve its runtime performance over time. [ABSTRACT FROM AUTHOR]

Agent-based modelling approaches are usually based on logical languages, whereas in many areas dynamical system models based on differential equations are used. This paper shows how to model complex agent systems, integrating quantitative, numerical and qualitative, logical aspects, and how to combine logical and mathematical analysis methods. [ABSTRACT FROM AUTHOR]

Interoperability has been broadly conceptualized as the ability of agents to work together. In open systems, the interoperability of agents is an important concern. A common way of achieving interoperability is by requiring agents to follow prescribed protocols in their interactions with others. In existing systems, agents must follow any protocol to the letter; in other words, they should exchange messages exactly as prescribed by the protocol. This is an overly restrictive constraint; it results in rigid, fragile implementations and curbs the autonomy of agents. For example, a customer agent may send a reminder to a merchant agent to deliver the promised goods. However, if reminders are not supported explicitly in the protocol they are enacting, then the reminder would be considered illegal and the transaction may potentially fail. This paper studies the interoperation of agents, dealing with their autonomy and heterogeneity in computational terms. [ABSTRACT FROM AUTHOR]

Formal specifications of protocol-oriented agent interactions have focused mainly on the semantics of the constituent agent communication language (ACL). In existing work, the semantics of a conversation policy is derived from the semantics of its individual communicative actions (CA) and there is no notion of persistency and compliance to the whole conversation policy. We argue that a proper theoretical treatment of conversations cannot be simply derived compositionally from the semantics of individual CAs. Accordingly, we develop a theory of joint conversations that is independent of its constituent CAs. We treat the process of a group following an interaction protocol as a persistent joint communicative action (JCA) by the group. This paper specifies the $\mathcal L_{JCA}$ logic based on Cohen and Levesque 1990 joint intention (JI) theory [2] and develops a framework in $\mathcal L_{JCA}$ logic for representing and reasoning about joint conversations. We define compliance in a joint conversation and we prove salient properties of joint conversations. Amongst others, we prove the existence of a Nash equilibrium in a bilateral interaction, and that our framework ensures an agent's compliance to the rules of the interaction in the sense that each participant jointly intends to uphold the whole conversation and to adhere to the conversation policy. [ABSTRACT FROM AUTHOR]

The use of agent-oriented models in developing complex, distributed, open, heterogeneous software is advocated. Agent-oriented models at the analysis level and design level are described, and a case study presented. We muse how modelling activity relates to the classical debate of whether knowledge is declarative or procedural. [ABSTRACT FROM AUTHOR]

We provide new perspectives on the semantics of logic programs with constraints. To this end we introduce several notions of computation and propose to use the results of computations as answer sets of programs with constraints. We discuss the rationale behind different classes of computations and study the relationships among them and among the corresponding concepts of answer sets. The proposed semantics generalize the answer set semantics for programs with monotone, convex and/or arbitrary constraints described in the literature. [ABSTRACT FROM AUTHOR]

In this paper, we propose a collaborative framework to realize a Virtual Enterprise (VE) for the domain of Micro Assembly. The framework is developed using 3APL technologies [7] and employs the idea of viewing WebService composition as a planning problem [8]. We describe the implementation of the framework and experiment with two micro assembly work cells. [ABSTRACT FROM AUTHOR]

The paper introduces the notion of off-line justification for Answer Set Programming (ASP). Justifications provide a graph-based explanation of the truth value of an atom w.r.t. a given answer set. The notion of justification accounts for the specifics of answer set semantics. The paper extends also this notion to provide justification of atoms during the computation of an answer set (on-line justification), and presents an integration of on-line justifications within the computation model of Smodels. Justifications offer a basic data structure to support methodologies and tools for debugging answer set programs. A preliminary implementation has been developed in $\mathbb{ASP-PROLOG}$. [ABSTRACT FROM AUTHOR]

We report on the development of an agent-based system, called ΦLOG, for the specification and execution of phylogenetic inference applications. We detail the implementation of the main components of the system. In the process, we discuss how advanced techniques developed in different research areas such as domain-specific languages, planning, Web Services discovery and invocation, and Web Service compositions can be applied in the building of the ΦLOG system. [ABSTRACT FROM AUTHOR]

In this paper we extend the high level execution language ConGolog (developed at the University of Toronto) by adding to it a new construct which we call the htn-construct. The new construct improves ConGolog by allowing easy specification of non-determinism when a partial ordering between a set of actions needs to be maintained. Furthermore, it allows temporal constraints to be specified easily. We present an implementation of the htn-construct in PROLOG which can be directly added to PROLOG implementations of ConGolog interpreters. [ABSTRACT FROM AUTHOR]